Low-intensity pulsed ultrasound/nanomechanical force generators enhance osteogenesis of BMSCs through microfilaments and TRPM7.

BACKGROUND: Low-intensity pulsed ultrasound (LIPUS) has been reported to accelerate fracture healing, but the mechanism is unclear and its efficacy needs to be further optimized. Ultrasound in combination with functionalized microbubbles has been shown to induce local shear forces and controllable mechanical stress in cells, amplifying the mechanical effects of LIPUS. Nanoscale lipid bubbles (nanobubbles) have high stability and good biosafety. However, the effect of LIPUS combined with functionalized nanobubbles on osteogenesis has rarely been studied. RESULTS: In this study, we report cyclic arginine-glycine-aspartic acid-modified nanobubbles (cRGD-NBs), with a particle size of ~ 500 nm, able to actively target bone marrow mesenchymal stem cells (BMSCs) via integrin receptors. cRGD-NBs can act as nanomechanical force generators on the cell membrane, and further enhance the BMSCs osteogenesis and bone formation promoted by LIPUS. The polymerization of actin microfilaments and the mechanosensitive transient receptor potential melastatin 7 (TRPM7) ion channel play important roles in BMSCs osteogenesis promoted by LIPUS/cRGD-NBs. Moreover, the mutual regulation of TRPM7 and actin microfilaments promote the effect of LIPUS/cRGD-NBs. The extracellular Ca2 + influx, controlled partly by TRPM7, could participated in the effect of LIPUS/cRGD-NBs on BMSCs. CONCLUSIONS: The nanomechanical force generators cRGD-NBs could promote osteogenesis of BMSCs and bone formation induced by LIPUS, through regulation TRPM7, actin cytoskeleton, and intracellular calcium oscillations. This study provides new directions for optimizing the efficacy of LIPUS for fracture healing, and a theoretical basis for the further application and development of LIPUS in clinical practice.

Decline of p300 contributes to cell senescence and growth inhibition of hUC-MSCs through p53/p21 signaling pathway.

Human umbilical cord-derived mesenchymal stromal cells (hUC-MSCs) in vitro expansion for long term may undergo epigenetic and genetic alterations that subsequently induce cellular senescence and associated growth inhibition. Increasing evidence implicated that aberrant histone acetylation modulates gene expression responsible for MSCs aging. Whether the dysregulation of p300 and its KAT activity is involved in the aging process of MSCs was still unexplored. In this study, we found a significant decrease of p300 but elevated p53/p21 levels in senescent hUC-MSCs at late-passage. Then we used two different approaches: (i) downregulation of p300 by siRNA and (ii) inhibition of the acetyltransferase(KAT) activity by C646 to determine the role of p300 in regulating MSCs senescence. We showed that inhibition of p300 induce premature senescence and decrease proliferation potential in hUC-MSCs. Moreover, upregulations of p53 and p21 expressions were confirmed in p300 knockdown and C646-treated hUC-MSCs. Taken together, these results suggest that p300 plays an important role in aging process of MSCs associated with activation of p53/p21 signaling pathway.

Reversibly immortalized human umbilical cord-derived mesenchymal stem cells (UC-MSCs) are responsive to BMP9-induced osteogenic and adipogenic differentiation.

Human mesenchymal stem cells (MSCs) are a heterogeneous subset of nonhematopoietic multipotent stromal stem cells and can differentiate into mesodermal lineage, such as adipocytes, osteocytes, and chondrocytes, as well as ectodermal and endodermal lineages. Human umbilical cord (UC) is one of the most promising sources of MSCs. However, the molecular and cellular characteristics of UC-derived MSCs (UC-MSCs) require extensive investigations, which are hampered by the limited lifespan and the diminished potency over passages. Here, we used the piggyBac transposon-based simian virus 40 T antigen (SV40T) immortalization system and effectively immortalized UC-MSCs, yielding the iUC-MSCs. A vast majority of the immortalized lines are positive for MSC markers but not for hematopoietic markers. The immortalization phenotype of the iUC-MSCs can be effectively reversed by flippase recombinase-induced the removal of SV40T antigen. While possessing long-term proliferation capability, the iUC-MSCs are not tumorigenic in vivo. Upon bone morphogenetic protein 9 (BMP9) stimulation, the iUC-MSC cells effectively differentiate into osteogenic, chondrogenic, and adipogenic lineages both in vitro and in vivo, which is indistinguishable from that of primary UC-MSCs, indicating that the immortalized UC-MSCs possess the characteristics similar to that of their primary counterparts and retain trilineage differentiation potential upon BMP9 stimulation. Therefore, the engineered iUC-MSCs should be a valuable alternative cell source for studying UC-MSC biology and their potential utilities in immunotherapies and regenerative medicine.

Mining Prognostic Significance of MEG3 in Human Breast Cancer Using Bioinformatics Analysis.

BACKGROUND/AIMS: Maternally expressed gene 3 (MEG3) is an imprinted gene with maternal expression, which may function as a tumor suppressor by inhibiting angiogenesis. To identify the prognostic value of MEG3 in breast cancer, systematic analysis was performed in this study. METHODS: To evaluate gene alteration during breast carcinogenesis, we explored MEG3 expression using the Serial Analysis of Gene Expression Genie suite and Oncomine analysis. The prognostic roles of MEG3 in breast cancer were investigated using the PrognoScan database. The heat map and methylation status of MEG3 were determined using the UCSC Genome Browser. RESULTS: We found that MEG3 was more frequently downregulated in breast cancer than in normal tissues and this correlated with prognosis. However, estrogen receptor and progesterone receptor status were found to be positively correlated with MEG3 expression. Conversely, basal-like status, triple-negative breast cancer status, and Scarff Bloom & Richardson grade criterion were negatively correlated with MEG3 expression. Following data mining in multiple big data databases, we confirmed a positive correlation between MEG3 and heparan sulfate proteoglycan 2 (HSPG2) expression in breast cancer tissues. CONCLUSION: MEG3 could be adopted as a marker to predict the prognosis of breast cancer with HSPG2. However, large-scale and comprehensive research is needed to clarify our results.

C6 glioma-conditioned medium induces malignant transformation of mesenchymal stem cells: Possible role of S100B/RAGE pathway.

Mesenchymal stem cells (MSCs) have been widely studied as an attractive therapeutic agent for the treatment of tumors. However, the adverse effects of the tumor paracrine factors who affect MSCs are still unclear. In this study, we report for the first time that C6 glioma-conditioned medium (GCM) induces malignant transformation of MSCs. In contrast to MSCs, the transformed mesenchymal stem cells (TMCs) exhibited tumor cell characterizations in vitro and highly tumorigenic in vivo. Furthermore, GCM and recombinant S100B increased receptor for advanced glycation end products (RAGE) and its downstream Akt1, STAT3 genes expression as well as phosphorylation and transcriptional activation. Finally, blockage of S100B-RAGE interaction by RAGE inhibitor FPS-ZM1 attenuated GCM and S100B-induced Akt1, STAT3 activation, abolished its cell proliferation, migration and invasion actions. Together, these results suggest that the RAGE pathway may play a possible role in malignant transformation procedure of MSCs, and that this process may be mediated through S100B.

BMP9 induces osteogenesis and adipogenesis in the immortalized human cranial suture progenitors from the patent sutures of craniosynostosis patients.

The cranial suture complex is a heterogeneous tissue consisting of osteogenic progenitor cells and mesenchymal stem cells (MSCs) from bone marrow and suture mesenchyme. The fusion of cranial sutures is a highly coordinated and tightly regulated process during development. Craniosynostosis is a congenital malformation caused by premature fusion of cranial sutures. While the progenitor cells derived from the cranial suture complex should prove valuable for studying the molecular mechanisms underlying suture development and pathogenic premature suture fusion, primary human cranial suture progenitors (SuPs) have limited life span and gradually lose osteoblastic ability over passages. To overcome technical challenges in maintaining sufficient and long-term culture of SuPs for suture biology studies, we establish and characterize the reversibly immortalized human cranial suture progenitors (iSuPs). Using a reversible immortalization system expressing SV40 T flanked with FRT sites, we demonstrate that primary human suture progenitor cells derived from the patent sutures of craniosynostosis patients can be efficiently immortalized. The iSuPs maintain long-term proliferative activity, express most of the consensus MSC markers and can differentiate into osteogenic and adipogenic lineages upon BMP9 stimulation in vitro and in vivo. The removal of SV40 T antigen by FLP recombinase results in a decrease in cell proliferation and an increase in the endogenous osteogenic and adipogenic capability in the iSuPs. Therefore, the iSuPs should be a valuable resource to study suture development, intramembranous ossification and the pathogenesis of craniosynostosis, as well as to explore cranial bone tissue engineering.

Notch Signaling Augments BMP9-Induced Bone Formation by Promoting the Osteogenesis-Angiogenesis Coupling Process in Mesenchymal Stem Cells (MSCs).

BACKGROUND/AIMS: Mesenchymal stem cells (MSCs) are multipotent progenitors that can differentiate into several lineages including bone. Successful bone formation requires osteogenesis and angiogenesis coupling of MSCs. Here, we investigate if simultaneous activation of BMP9 and Notch signaling yields effective osteogenesis-angiogenesis coupling in MSCs. METHODS: Recently-characterized immortalized mouse adipose-derived progenitors (iMADs) were used as MSC source. Transgenes BMP9, NICD and dnNotch1 were expressed by adenoviral vectors. Gene expression was determined by qPCR and immunohistochem¡stry. Osteogenic activity was assessed by in vitro assays and in vivo ectopic bone formation model. RESULTS: BMP9 upregulated expression of Notch receptors and ligands in iMADs. Constitutively-active form of Notch1 NICD1 enhanced BMP9-induced osteogenic differentiation both in vitro and in vivo, which was effectively inhibited by dominant-negative form of Notch1 dnNotch1. BMP9- and NICD1-transduced MSCs implanted with a biocompatible scaffold yielded highly mature bone with extensive vascularization. NICD1 enhanced BMP9-induced expression of key angiogenic regulators in iMADs and Vegfa in ectopic bone, which was blunted by dnNotch1. CONCLUSION: Notch signaling may play an important role in BMP9-induced osteogenesis and angiogenesis. It's conceivable that simultaneous activation of the BMP9 and Notch pathways should efficiently couple osteogenesis and angiogenesis of MSCs for successful bone tissue engineering.

The evolving roles of canonical WNT signaling in stem cells and tumorigenesis: implications in targeted cancer therapies.

The canonical WNT/ß-catenin signaling pathway governs a myriad of biological processes underlying the development and maintenance of adult tissue homeostasis, including regulation of stem cell self-renewal, cell proliferation, differentiation, and apoptosis. WNTs are secreted lipid-modified glycoproteins that act as short-range ligands to activate receptor-mediated signaling pathways. The hallmark of the canonical pathway is the activation of ß-catenin-mediated transcriptional activity. Canonical WNTs control the ß-catenin dynamics as the cytoplasmic level of ß-catenin is tightly regulated via phosphorylation by the 'destruction complex', consisting of glycogen synthase kinase 3ß (GSK3ß), casein kinase 1α (CK1α), the scaffold protein AXIN, and the tumor suppressor adenomatous polyposis coli (APC). Aberrant regulation of this signaling cascade is associated with varieties of human diseases, especially cancers. Over the past decade, significant progress has been made in understanding the mechanisms of canonical WNT signaling. In this review, we focus on the current understanding of WNT signaling at the extracellular, cytoplasmic membrane, and intracellular/nuclear levels, including the emerging knowledge of cross-talk with other pathways. Recent progresses in developing novel WNT pathway-targeted therapies will also be reviewed. Thus, this review is intended to serve as a refresher of the current understanding about the physiologic and pathogenic roles of WNT/ß-catenin signaling pathway, and to outline potential therapeutic opportunities by targeting the canonical WNT pathway.

The Calcium-Binding Protein S100A6 Accelerates Human Osteosarcoma Growth by Promoting Cell Proliferation and Inhibiting Osteogenic Differentiation.

BACKGROUND/AIMS: Although osteosarcoma (OS) is the most common primary malignancy of bone, its molecular pathogenesis remains to be fully understood. We previously found the calcium-binding protein S100A6 was expressed in ∼80% of the analyzed OS primary and/or metastatic tumor samples. Here, we investigate the role of S100A6 in OS growth and progression. METHODS: S100A6 expression was assessed by qPCR and Western blotting. Overexpression or knockdown of S100A6 was carried out to determine S100A6's effect on proliferation, cell cycle, apoptosis, tumor growth, and osteogenic differentiation. RESULTS: S100A6 expression was readily detected in human OS cell lines. Exogenous S100A6 expression promoted cell proliferation in vitro and tumor growth in an orthotopic xenograft model of human OS. S100A6 overexpression reduced the numbers of OS cells in G1 phase and increased viable cells under serum starvation condition. Conversely, silencing S100A6 expression induced the production of cleaved caspase 3, and increased early stage apoptosis. S100A6 knockdown increased osteogenic differentiation activity of mesenchymal stem cells, while S100A6 overexpression inhibited osteogenic differentiation. BMP9-induced bone formation was augmented by S100A6 knockdown. CONCLUSION: Our findings strongly suggest that S100A6 may promote OS cell proliferation and OS tumor growth at least in part by facilitating cell cycle progression, preventing apoptosis, and inhibiting osteogenic differentiation. Thus, it is conceivable that targeting S100A6 may be exploited as a novel anti-OS therapy.

An Overview of Current Statistical Methods for Implementing Quality Tolerance Limits.

BACKGROUND: In 2016, the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use updated its efficacy guideline for good clinical practice and introduced predefined quality tolerance limits (QTLs) as a quality control in clinical trials. QTLs are complementary to Quality by Design (QbD) principles (ICH-E8) and are one of the components of the risk-based clinical trial quality management system. METHODS: Currently the framework for QTLs process is well established, extensively describing the operational aspects of Defining, Monitoring and Reporting, but a single source of commonly used methods to establish QTLs and secondary limits is lacking. This paper will primarily focus on closing this gap and include applications of statistical process control and Bayesian methods on commonly used study level quality parameters such as premature treatment discontinuation, study discontinuation and significant protocol deviations as examples. CONCLUSIONS: Application of quality tolerance limits to parameters that correspond to critical to quality factors help identify systematic errors. Some situations pose special challenges to implementing QTLs and not all methods are optimal in every scenario. Early warning signals, in addition to QTL, are necessary to trigger actions to further minimize the possibility of an end-of-study excursion.

Erratum: [Corrigendum] Hepa1­6­FLuc cell line with the stable expression of firefly luciferase retains its primary properties with promising bioluminescence imaging ability.

[This corrects the article DOI: 10.3892/ol.2018.8132.].

PINK1 contained in huMSC-derived exosomes prevents cardiomyocyte mitochondrial calcium overload in sepsis via recovery of mitochondrial Ca2+ efflux.

BACKGROUND: Sepsis is a systemic inflammatory response to a local severe infection that may lead to multiple organ failure and death. Previous studies have shown that 40-50% of patients with sepsis have diverse myocardial injuries and 70 to 90% mortality rates compared to 20% mortality in patients with sepsis without myocardial injury. Therefore, uncovering the mechanism of sepsis-induced myocardial injury and finding a target-based treatment are immensely important. OBJECTIVE: The present study elucidated the mechanism of sepsis-induced myocardial injury and examined the value of human umbilical cord mesenchymal stem cells (huMSCs) for protecting cardiac function in sepsis. METHODS: We used cecal ligation and puncture (CLP) to induce sepsis in mice and detect myocardial injury and cardiac function using serological markers and echocardiography. Cardiomyocyte apoptosis and heart tissue ultrastructure were detected using TdT-mediated dUTP Nick-End Labeling (TUNEL) and transmission electron microscopy (TEM), respectively. Fura-2 AM was used to monitor Ca2+ uptake and efflux in mitochondria. FQ-PCR and Western blotting detected expression of mitochondrial Ca2+ distribution regulators and PTEN-induced putative kinase 1 (PINK1). JC-1 was used to detect the mitochondrial membrane potential (Δψm) of cardiomyocytes. RESULTS: We found that expression of PINK1 decreased in mouse hearts during sepsis, which caused cardiomyocyte mitochondrial Ca2+ efflux disorder, mitochondrial calcium overload, and cardiomyocyte injury. In contrast, we found that exosomes isolated from huMSCs (huMSC-exo) carried Pink1 mRNA, which could be transferred to recipient cardiomyocytes to increase PINK1 expression. The reduction in cardiomyocyte mitochondrial calcium efflux was reversed, and cardiomyocytes recovered from injury. We confirmed the effect of the PINK1-PKA-NCLX axis on mitochondrial calcium homeostasis in cardiomyocytes during sepsis. CONCLUSION: The PINK1-PKA-NCLX axis plays an important role in mitochondrial calcium efflux in cardiomyocytes. Therefore, PINK1 may be a therapeutic target to protect cardiomyocyte mitochondria, and the application of huMSC-exo is a promising strategy against sepsis-induced heart dysfunction.

Dynamic effect of di-2-(ethylhexyl) phthalate on testicular toxicity: epigenetic changes and their impact on gene expression.

This study investigated epigenetic (specifically, DNA methylation) changes and their impact on gene expression in testes induced by maternal exposure to Di-2-(ethylhexyl) phthalate (DEHP) in mice. Testicular dysgenesis syndrome was induced in fetuses and pups by maternal exposure to DEHP at 500 mg/kg/d, and testes were excised for analysis on gestation day (GD) 19 and postnatal days (PNDs) 3, 21, 56, and 90. High-performance liquid chromatography (HPLC) was performed to analyze DNA methylation status, and expression levels of the DNA methyltransferases were examined by quantitative real-time polymerase chain reaction (qPCR). Testis-specific gene, insulin-like hormone 3 (Insl3), and testosterone production were also detected. DEHP significantly increased DNA methylation levels on GD 19 and PND 3 (P < .05 and P < .05) but not on PNDs 21, 56, and 90. DEHP also significantly increased the expression of DNA methyltransferases. For DNA methyltransferase 1, the difference was not significant on PND 21, and DNA methyltransferase 3a and 3b returned to normal levels on PND 56. Fetal testes were a main target for DEHP as evidenced by a reduction in Insl3 expression and testosterone production. Effects of DEHP on Insl3 expression continued until PND 21. The DEHP-induced suppression of testosterone had not recovered on PND 56. Changes in DNA methylation may play an important role in abnormal testicular function caused by environmental factors such as maternal exposure to DEHP, which may be a mechanism of DEHP-mediated testicular toxicity.

[Di-(2-ethylhexyl) phthalate increases the DNA methylation level of genomes in the mouse testis].

OBJECTIVE: To investigate the effect of the exposure to di- (2-ethylhexyl) phthalate (DEHP) during pregnancy on the DNA methylation level of genomes in the testis of the offspring in mice. METHODS: Pregnant KM mice were randomly divided into three groups, normal control, corn oil and DEHP-exposed. Corn oil and DEHP (500 mg/[kg x d]) were administrated respectively from gestation day 12.5 (GD 12.5) to postnatal day 3 (PND 3). The testes of the offspring were excised on PND 7, and their genomic DNA was treated with EcoR I /Msp I and EcoR I /Hpa II. The genome-wide DNA methylation patterns of the CCGG sites were detected by methylation-sensitive amplification polymorphism (MSAP). The samples were electrophoresed in the ABI 3730 DNA sequencer and the results analyzed by the Genescan3.1. RESULTS: The average incidence of DNA methylation was (34.03 +/- 3.05)% in the DEHP-exposed mice, obviously higher than (28.37 +/- 2.37)% in the normal control and (28.58 2.45)% in the corn oil group, with statistically significant differences (P < 0.05). CONCLUSION: Exposure to DEHP during pregnancy increases the DNA methylation level of the genome in the testis of the offspring and affects the apparent genetic modification of the genome, which may be one of the important toxicological causes of the lesion in the reproductive system.

Changes in the expression and subcellular localization of RARalpha in the rat hippocampus during postnatal development.

Retinoic acid receptors (RARs) are reported to mediate the effects of retinoid acid and participate in the maintenance of normal hippocampal function during embryonic and postnatal stages. RARalpha is the only one that has been reported to be continuously expressed among RARs in the CA1-CA3 areas of the hippocampus, at both the mRNA and the protein level. Here, we show the expression and subcellular localization of RARalpha in granule and pyramidal cells in various regions of the hippocampus during postnatal development of rats. We discovered that the expression level of RARalpha in postnatal hippocampal tissue gradually decreased over time with increasing developmental maturity of the nervous system. Moreover, the subcellular localization of RARalpha expression showed a phenomenon of intracellular translocation during the postnatal development period. This new discovery is inconsistent with a traditional viewpoint according to which RARalpha, as a nuclear transcription factor, is mainly expressed inside nucleus. This phenomenon suggests that RARalpha may have different actions during each stage of hippocampal development.

Hepa1-6-FLuc cell line with the stable expression of firefly luciferase retains its primary properties with promising bioluminescence imaging ability.

Reliable animal models are required for the in vivo study of the molecular mechanisms and effects of chemotherapeutic drugs in hepatocarcinoma. In vivo tracing techniques based on firefly luciferase (FLuc) may optimize the non-invasive monitoring of experimental animals. The present study established a murine Hepa1-6-FLuc cell line that stably expressed a retrovirus-delivered FLuc protein gene. The cell morphology, proliferation, migration and invasion ability of Hepa1-6-FLuc cells were the same as that of the Hepa1-6 cells, and thus is suitable to replace Hepa1-6 cells in the construction of hepatocarcinoma animal models. No differences in subcutaneous tumor mass and its pathomorphology from implanted Hepa1-6-FLuc cells were observed compared with Hepa1-6 control tumors. Bioluminescence imaging indicated that the Luc signal of the Hepa1-6-FLuc cells was consistently strengthened with increases in tumor mass; however, the Luc signal of Hepa1-6-AdFLuc became weaker and eventually disappeared during tumor development. Therefore, compared with the transient expression by adenovirus, stable expression of the FLuc gene in Hepa1-6 cells may better reflect cell proliferation and survival in vivo, and provide a reliable source for the establishment of hepatocarcinoma models.

Adenovirus-Mediated Gene Delivery: Potential Applications for Gene and Cell-Based Therapies in the New Era of Personalized Medicine.

With rapid advances in understanding molecular pathogenesis of human diseases in the era of genome sciences and systems biology, it is anticipated that increasing numbers of therapeutic genes or targets will become available for targeted therapies. Despite numerous setbacks, efficacious gene and/or cell-based therapies still hold the great promise to revolutionize the clinical management of human diseases. It is wildly recognized that poor gene delivery is the limiting factor for most in vivo gene therapies. There has been a long-lasting interest in using viral vectors, especially adenoviral vectors, to deliver therapeutic genes for the past two decades. Among all currently available viral vectors, adenovirus is the most efficient gene delivery system in a broad range of cell and tissue types. The applications of adenoviral vectors in gene delivery have greatly increased in number and efficiency since their initial development. In fact, among over 2,000 gene therapy clinical trials approved worldwide since 1989, a significant portion of the trials have utilized adenoviral vectors. This review aims to provide a comprehensive overview on the characteristics of adenoviral vectors, including adenoviral biology, approaches to engineering adenoviral vectors, and their applications in clinical and pre-clinical studies with an emphasis in the areas of cancer treatment, vaccination and regenerative medicine. Current challenges and future directions regarding the use of adenoviral vectors are also discussed. It is expected that the continued improvements in adenoviral vectors should provide great opportunities for cell and gene therapies to live up to its enormous potential in personalized medicine.

CRISPR/Cas9-mediated reversibly immortalized mouse bone marrow stromal stem cells (BMSCs) retain multipotent features of mesenchymal stem cells (MSCs).

Mesenchymal stem cells (MSCs) are multipotent non-hematopoietic progenitor cells that can undergo self-renewal and differentiate into multi-lineages. Bone marrow stromal stem cells (BMSCs) represent one of the most commonly-used MSCs. In order to overcome the technical challenge of maintaining primary BMSCs in long-term culture, here we seek to establish reversibly immortalized mouse BMSCs (imBMSCs). By exploiting CRISPR/Cas9-based homology-directed-repair (HDR) mechanism, we target SV40T to mouse Rosa26 locus and efficiently immortalize mouse BMSCs (i.e., imBMSCs). We also immortalize BMSCs with retroviral vector SSR #41 and establish imBMSC41 as a control line. Both imBMSCs and imBMSC41 exhibit long-term proliferative capability although imBMSC41 cells have a higher proliferation rate. SV40T mRNA expression is 130% higher in imBMSC41 than that in imBMSCs. However, FLP expression leads to 86% reduction of SV40T expression in imBMSCs, compared with 63% in imBMSC41 cells. Quantitative genomic PCR analysis indicates that the average copy number of SV40T and hygromycin is 1.05 for imBMSCs and 2.07 for imBMSC41, respectively. Moreover, FLP expression removes 92% of SV40T in imBMSCs at the genome DNA level, compared with 58% of that in imBMSC41 cells, indicating CRISPR/Cas9 HDR-mediated immortalization of BMSCs can be more effectively reversed than that of retrovirus-mediated random integrations. Nonetheless, both imBMSCs and imBMSC41 lines express MSC markers and are highly responsive to BMP9-induced osteogenic, chondrogenic and adipogenic differentiation in vitro and in vivo. Thus, the engineered imBMSCs can be used as a promising alternative source of primary MSCs for basic and translational research in the fields of MSC biology and regenerative medicine.

Noncanonical Wnt signaling plays an important role in modulating canonical Wnt-regulated stemness, proliferation and terminal differentiation of hepatic progenitors.

The liver provides vital metabolic, exocrine and endocrine functions in the body as such pathological conditions of the liver lead to high morbidity and mortality. The liver is highly regenerative and contains facultative stem cells that become activated during injury to replicate to fully recover mass and function. Canonical Wnt/ß-catenin signaling plays an important role in regulating the proliferation and differentiation of liver progenitor cells during liver regeneration. However, possible roles of noncanonical Wnts in liver development and regeneration remain undefined. We previously established a reversibly-immortalized hepatic progenitor cell line (iHPx), which retains hepatic differentiation potential. Here, we analyze the expression pattern of the essential components of both canonical and noncanonical Wnt signaling pathways at different postnatal stages of mouse liver tissues and iHPx cells. We find that noncanonical Wnt4, Wnt5a, Wnt9b, Wnt10a and Wnt10b, are highly expressed concordantly with the high levels of canonical Wnts in late stages of liver tissues. Wnt5a, Wnt9b, Wnt10a and Wnt10b are able to antagonize Wnt3a-induced ß-catenin/TCF activity, reduce the stemness of iHPx cells, and promote hepatic differentiation of liver progenitors. Stem cell implantation assay demonstrates that Wnt5a, Wnt9b, Wnt10a and Wnt10b can inhibit cell proliferation and promote hepatic differentiation of the iHPx progenitor cells. Our results strongly suggest that noncanonical Wnts may play an important role in fine-tuning Wnt/ß-catenin functions during liver development and liver regeneration. Thus, understanding regulatory mechanisms governing proliferation and differentiation of liver progenitor cells may hold great promise to facilitate liver regeneration and/or progenitor cell-based therapies for liver diseases.